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OFDM communication system and transmitter-receiver for use in the system

Active Publication Date: 2006-08-29
DENSO CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013]The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved OFDM communication system using transmission diversity, in which the signal phase is accurately adjusted and transmission can be performed with high efficiency.
[0017]Since the data signals are transmitted from and received by either one of two antennas having a higher performance for each sub-carrier frequency, and the received data signals are phase-adjusted using the pilot signals commonly included in both OFDM signals, the phase of the data signal is accurately adjusted at the receiving end, and communication can be efficiently performed.

Problems solved by technology

However, there is a following problem in the proposed diversity system.
If the signals under the same sub-carrier are sent from both antennas, the signals interferes with one another.
Since the signals transmitted through different routes have respectively different phase-rotations, the phase adjustment cannot be done accurately if the signals are handled as a single signal.

Method used

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  • OFDM communication system and transmitter-receiver for use in the system
  • OFDM communication system and transmitter-receiver for use in the system
  • OFDM communication system and transmitter-receiver for use in the system

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first embodiment

[0035]the present invention will be described with reference to FIGS. 1–7. Components shown in FIGS. 1–7 having the same reference numbers as those in FIGS. 10–12 are the same or substantially same components as those shown in FIGS. 10–12. First, referring to FIG. 1, an entire structure of the OFDM communication system using diversity transmission according to the present invention will be briefly described. A pair of antennas, a horizontal polarization antenna 10 and a vertical polarization antenna 11, are provided in a base terminal A. Similarly, a mobile terminal B includes a pair of antennas, a horizontal polarization antenna 110 and a vertical polarization antenna 111. By using horizontally polarized waves and vertically polarized waves, interferences between signals are avoided if same signals are sent using the same sub-carrier frequencies.

[0036]In the mobile terminal B, signals received through the horizontal polarization antenna 110 are FFT-processed by an FFT-processor 116...

second embodiment

[0051]Since, in the second embodiment, the same OFDM signals are transmitted and received through both antennas, the horizontal polarization antenna and the vertical polarization antenna, the OFDM signals are demodulated at the receiving end with high accuracy, even if the mobile terminal as the receiving end moves and changes its positions.

[0052]While the present invention has been shown and described with reference to the foregoing preferred embodiments, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims. For example, the phase adjusters 19, 20 in the first embodiment may adjust only the phase of signals of one branch having higher levels based on information from the signal level detector 18. Similarly, the phase adjusters 118, 119 in the second embodiment may adjust only the phase of signals of one branch having higher levels based on information f...

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Abstract

A diversity OFDM communication is performed between a base terminal and a mobile terminal, both having a horizontal polarization antenna and a vertical polarization antenna forming two transmission channels. In the base terminal, data signals to be transmitted are divided into two channels to transmit the data signals through either one of the channels having a higher transmission performance for each sub-carrier. Common pilot signals are transmitted through both channels. The data signals received by the mobile terminal are phase-adjusted using the common pilot signals. The phase-adjusted data signals in both channels are synthesized and then demodulated.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is based upon and claims benefit of priority of Japanese Patent Application No. 2000-164885 filed on Jun. 1, 2000, the content of which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) communication system and receiver-transmitters for use in the system as a base terminal and a mobile terminal.[0004]2. Description of Related Art[0005]It is generally known to use the OFDM communication system in MMAC (Multimedia Mobile Access Communication) as an effective transmission system under a multi-pass environment. To improve error rate performance in the OFDM communication system, transmission diversity techniques are proposed in an article entitled “A Study on Transmission Diversity for MMAC System” (SST99-87, pages 87–92), which is published in an technical report of The Institute of Electronic...

Claims

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Application Information

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IPC IPC(8): H04J11/00H04B7/10H04L7/00H04Q11/02
CPCH04Q11/02H04B7/10H04L27/2647H04L27/2626H04L5/0048
Inventor KUWABARA, MASAHIROSAWADA, MANABUSASAKI, KUNIHIKO
Owner DENSO CORP
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